Anode insulating structure



June 30,1953

w. w. wATRoUs, JR l ANODE INSULATNG STRUCTURE 2 Sheets-Sheet 1 Filed Dec. 29., 1950 fl/rrr/lr//l//lll//l/l/l INVENTOR. ,em/Www@ nnnannnnaa June 30, 1953 w. w. wATRoUs, JR

ANODE INSULATING STRUCTURE 2 Sheets-Sheet 2 Filed Dec. 29, 1950 'lll FAV f/f//l//l/l//l/l/w FIGA m w w. m

Patented June 30, 1953 lANODE INSULATING STRUCTURE Ward W. Watrous, Jr., Chatham, N. J .,assignor to Chatham Electronics Corporation, Newark, vN. J., a corporation of New Jersey Application December 29, 1950, Serial No. 203,439'

, Claims. 1

This invention relates to anode insulators as applied to gaseous discharge devices, and has particular reference to the structural mounting of anodes used in high voltage two and three element tubes.

The anode vmounting of a gaseous discharge device has always been a problem inthe design and operation of gas tubes at high voltage. Eficient high voltage rectiiiers usually employ a shield which encloses the anode as completely as possible. Three electrode gaseous'tubes also enclose the anode in a shield which is generally connected to the control electrode to insure adequate control of the cathode-anode current and eliminate conduction in the tube when the anode is at a negative potential.

However, the anode lead must be brought out of the lenclosing shield and envelope for electrical conduction; hence, the shield or the control electrode structure cannot completely sur` roundL the anode and there is always the possibility that a non-controllable glow discharge may be started ybetween the anode lead-in conductor and the other electrodes or shield. Such a'glow discharge generally starts over fa comparatively long path where ionization by collision is effected. The limitations of such a construction result in the use of an anode Voltage of 10,000 Volts or less.

During recent years the desire for higher voltage discharge devices has called for new designs and new systems. The anode structure hereinafter described withstands 40,000 volts between the anode and the combined cathode and control electrode. This discharge device operates at a peak current value of 2,500 amperes.

One of the objects of the invention is to provide an improved anode insulating structure which avoids one or more of the disadvantages and limitations of prior art arrangements.

Another object of the invention is to provide an improved insulating structure which can be operated at much higher `anode voltages than heretofore.

Another object of the invention is to provide ,an anode structure which can be assembled easily ,electrode structure.

The invention comprises an anode insulating structure for mounting an anode in a gaseous discharge device and includesa lead-in conductor forthe anode, a cylindrical conducting guard 2 secured to the anode and surrounding thelead-in conductor, and an inner cylindrical insulator surrounding the conducting guard. On the outside of the inner cylinder, which is'usually made .of glass, another insulating cylinder is mounted, and it is to this outer cylinder that the. enclosing shield is secured.

For a better understanding of the present invention, together with other and further objects thereof, reference is made to the following description taken in connectionwith the accompanying drawings.

Fig. l is a cross sectional viewof `one form of the anode insulating mounting.

Fig. 2 is a cross'secti'onal view of anotherform of the anode insulating structure.

Fig. 3 is a cross sectional view of a vthird Variation of the anode insulator.

Fig. 4 is a cross section taken of Fig. l. y

Referring now to Fig. l, an envelope I0 encloses the evacuated chamber and the electrodes.

along, line #+4 At the anode and a re-entrant portion II of the Vthe inner cylinder. cured to-the anode I6 and acts as a guardv to reduce the voltage gradient so that .the interior` envelope is employed to seal an outer cylindrical insulator I2 which, in turn, holds an:v anode lead-in conductor I3 by means of seal Hi at its upper end. An inner cylindrical insulator IE is also anchored atthe anode seal I4 and extends in axial alignment into the tube closely spaced from the outer cylinder. v

At the lower end of lead-in conductor I3.:a flat plate anode IB is securely mounted. The lower face of this electrode furnishes the conducting surface for the` electrical discharge when the tube is operated. A control electrode 20 and a baiile 2l are mounted below the anode, both beingmade of metallic conducting material. An enclosing structure surrounds the greater portion of the anode and includes a cylindrical portion 22, a flat disk 23 mounted above the anode I5, and a grid plate 20 below theanode.A To secure theshield and keep it always in alignment a clamping arrangement 24 is used to clamp lthe top portion of the shield to the outside surface of insulating cylinder I2. This clamping feature is made possible by the more rugged construction of this .type of structure. o

Inside the inner cylinder I5 a conducting cylindrical shell 25 is mounted in close proximity to The conducting shell is sevolume surrounding the conductor I3 is fieldv free and, therefore, there is no tendency 'for anfarc or brush discharge to `occur at the 'junction-of the support rod I3 and .thelglass bead. I

. The spacing between the shelllandtheinner insulator I5 is made as small as is convenient for the fabrication processes used. The spacing -between the inner insulator I5 and the outer insulator I2 is also made quite small, usually about .030 inch to cut down on the possibility of glow discharges.

Thesegaseous `discharge devices are iilled with hydrogen gas at a pressure range from 400 to 900 microns (of mercury) and, therefore, the ions have a mean free path of about one-:inchfand the electrons have a mean free'path of about six inches. At low voltages glow :discharges fshould not be expected at distances-shorter'than haii this distance but at 40,000 volts stray collisions may set up a discharge atg, o,n e tenth the mean free path. For this reason all ionizable paths ar kept as short as possible.

The anode insulating structure shown in Fig. 2 isfor smallerltubes and lower voltages. It .difEers fromnthestructure ofJFig. 1 in .that three 4cylindrical insulators fare .used instead of two and there is no static shield. The device has an anode lr6, .an inner .cylindrical insulator I5, an outer cylindrical insulator I2, and an intermedi-A ate insulator 30. The shield 23 is secured .to the outerinsulator in the usualmanner.

The design shown in Fig..3 is similar to that of Fig. 1v except that the outer insulating cylinder is limited. in length -and lextends .only from the upper shield disk 23 to the seal between the reentrant portion of the .envelope II and .thenner cylinder I5. In this A.manner .the length -o path .between .cylindersris shortened and the chances of an uncontrolled glow discharge are `greatly reduced. :Thedesign shown in Fig. 3 also differs from Fig. l in the arrangement of the lead-in seal and the outer rim of the re-entrant portion. The shield 25, innercylindrical insulator I5, and -seal |14 .are lowered .so that an insulating substance I:8, suchas wax, silicone jelly, or other sat- -isfactory insulating compound, may be employed to ll there-entrant cavity and completely cover the Vjunction between the bead I'I and the lead-in insulator I3.

When .the discharge device is in operation, thereis astrong electric field between conducting vshield 25 vand the .clamping structure "24. Most of the lines of force in this field are normal to .the surfaces of the shield and the clamp, but in thezvicinity of the shield Yplate 23 the electric field is concentrated at the position `3I where lthe shield plate is positioned nearestto the shield. Because ofthis concentration the'lower end 32 of insulating cylinder I2 is in an electric field which is ycomparatively weak and there is little or no tendency .at this lpoint to effect sparking due to v.the junction `of an insulator and a conductor.

The lower. end of insulating cylinder is in a strong .electric iieldbut touches no metal at or near this point.

From the `above .description it will be evident that `.the invention provides an anode structure which is sturdy, capable of withstanding Vhigh voltage, :and .efficient inradiating heat losses.

While there have been described and illustrated specific .embodiments of the invention, iti-Will be Y obvious .that various changes and modifications drical 4 surrounding the lead-in conductor, an inner cylindrical insulator surrounding the conducting guard, an outer cylindrical insulator surrounding the inner cylindrical insulator, and mounting means for securing an electrode on the outer cylindrical insula-tor.

2. 'An anode insulating structure for mounting an anode in a gaseous discharge device comprising, an anode lead-in conductor sealed in a glass envelopesfor supporting the anode, a cylindrical conducting v,guard secured to the anode and surrcundigng'the lead-in conductor, an inner cylininsulator surrounding the conducting guard, an outer cylindrical insulator surrounding .the inner :cylindrical insulator. and clamping means onthe outer cylindrical insulator for securingr'a low voltage metallic shield.

3. An anode insulating structure for mounting :and .insulating the anode ina gaseous .discharge device comprising, .an anode lead-in .conductor sealed lin ;a V.glass .envelope Vfor supporting .the anodaa :cylindrical conduct-ing. guard secured to the anode and surrounding the lead-in conductor, :an inner cylindrical glass Kinsulator secured to -theglass envelope and :surrounding the conductingguard, ian outer cylindrical glass insulator .also secured to .the glass .envelope and surrounding the inner cylindrical insulator, and clamping means onthe outer cylindrical insula- .torvfor securinga -low voltage metallic shield.

4. An anode :insulating `struc-ture rfor mounting ahigh .voltageanode of a gaseous discharge device comprising, an anode lead-inV conductor sealed in a glass envelope for Vsupporting the anode and lproviding -an electrical connection to anexternal source .of power, a cylindrical conducting guard secured y'to .the anode and surroundingthe lead-in conductor, an inner cylindrical glass ,insulator secured to the glass envelope and surrounding Vthe cylindrical conduct-ing guard in close proximity thereto, an outer cylindrical glass` insulator also secured to Athe glass envelope and surrounding the inner cylindrical .insulator in-close'proximity thereto, and clamping Ameans on the outer cylindrical insulator for securinga low voltage metallic shield.

5. vAnanode :insulating structure for mounting va .high voltage anodeof a :gaseous discharge device comprising, an anode lead-in conductor sealed lin a glass envelope for supporting the .anodeand providing an electrical connection vto an .external source .of power, a cylindrical conducting guard secured .to vthe anode and sur rounding .the-'lead-in conductor, an inner cylindrical glass? insulator ysecured to the glass envelope. and :surrounding .the :cylindrical conducting guard with aspacing from'saidgua'rd of less `than one-.tenth of the-.mean free-path ofthe gas within the Vdischarge device, `anouter cylindrical glass insulator -also secured :to .the glass envelope and surrounding the inner cylindrical insulator with a spacing from -saidinner1insulator of less than onetenth :of fthe-'mean free lpath of theffgas, and clamping .means on ttheouter` cylindrical insulatorior securing va Llow `voltage metallic shield.

References'iteil in the `file nof thispatent uNrfED- ,STATES PATENTS Number Name Date 2,320,949 Myers et al June 1, Li943 "2,404,413 Stutsman July .23, 1946 2,463,577 Stutsman fMar. f8, 1949 vfzgliillff ,Sloan Dec. 27, 1949 

